1. Field of the Invention
The present invention relates to a handwriting code processing device enabling reduction in load on processing of an input device which electronically realizes operability of writing utensils that paper and a pen produce by coding handwriting input by a user at high efficiency without reducing power of expression which handwritings have, and a processing method thereof.
2. Description of the Related Art
There is an increasing demand, as an input means of a portable terminal device for general users, for an input device which realizes operability of writing utensils that paper and a pen produce by combining a touch panel and a display device (hereinafter referred to as a handwriting input display device). Among the reasons are that training of operation which is required for a keyboard and a mouse is unnecessary because inputting is possible by almost the same sense of operation as that of handwriting and that it is unnecessary to ensure working space for input operation which is required for a keyboard and a mouse because of direct operation to a display screen of the device.
Known as a conventional handwriting input coding technique employed in a handwriting input display device of this kind is zone-coding (CCITT recommendations T.150, JT-T. 150 standard in Japan). Zone-coding is a coding system making use of the characteristics that a vector indicative of a difference between two successive coordinate points in handwriting input is small in magnitude and small in direction change. Conventional handwriting code processing devices employing zone-coding such as a telewriting terminal realize high compressibility by variable-length codes on a bit basis.
The zone-coding system, however, has a shortcoming that since no coding is made of a succession of the same values, with respect to input without variation, the number of codes will be increased to increase the load on processing of the input device as a whole.
In addition, since compressibility is decreased as a difference vector calculated at coding is increased, sufficient compressibility could not be achieved depending on a precision of detection of handwriting input by a device. It is also difficult to appropriately display handwritings coded at input devices with different detection precisions.
Moreover, although precision of handwriting operation itself, such as unintentional movement of a user's hand, changes depending on the contents of handwriting operation, precision of data coded for the coordinate detection and displaying remains constant to fail to correspond to the contents of handwriting operation. Therefore, a rough line drawn quickly by a user, for example, will be detected with a higher precision than intended to output a large volume of codes, resulting in increasing the load on processing.
Furthermore, it is very difficult to edit part of coded data because code length and value can not be determined unless every point from the beginning of the coded data is decoded in sequence.
Another known conventional handwriting input coding technique is a still picture coding system which detects and codes a period of a succession of the same values. An example of a coding technique of this kind is recited in Japanese Patent Laying-Open (Kokai) No. Heisei 3-163961, entitled "Image Compression Method". The literature discloses an image compression method of obtaining compressed data from multivalued image data by discriminating, as to multivalued image data obtained by scanning image and sampling on an image basis, a period when the same concentration level continues from a period when concentration level change succeeds one after another and converting the multivalued image data in the period when the same concentration level continues into a code peculiar to a length of the period.
Increasing compressibility for handwriting information coding by applying such a general-purpose coding system as recited in the above literature might result in losing the order of or the amount of change in a sequence of coordinate points of handwriting input in some cases because characteristics of handwriting input data and those of still picture data differ from each other. As a result, it is impossible to employ such handwriting reproduction processing with reduced processing load which makes use of the characteristics of user's handwriting operation as recited in Japanese Patent Laying-Open (Kokai) No. Heisei 9-190275 (corresponding U.S. patent application Ser. No. 08/781,807), entitled "Handwriting Input Display Device", making rapid-response displays difficult, as well as degrading quality of handwriting displays.
Japanese Patent Laying-Open (Kokai) No. Heisei 9-190275 discloses a handwriting input display device including a subsequent input point predicting means for generating a predicted coordinate point for each coordinate point received from an input means in order to reduce a delay time from handwriting input made by a user until execution of response display, a point of passage predicting means for receiving a sequence of coordinate points from the subsequent input point predicting means to insert a new sequence of coordinate points between adjacent coordinate points in order to output a sequence of coordinate points forming a smooth handwritten curve, and a processing means for instructing the subsequent input point predicting means on a calculation method for generating a predicted coordinate point and instructing the point of passage predicting means on a coordinate point insertion method to display a curve based on a sequence of coordinate points obtained from the point of passage predicting means on a display means.
As described in the foregoing, handwriting code processing techniques employed in conventional handwriting input display devices fail to sufficiently realize such facility as that of actual paper and pens.